Diiodoperfluoroalkanes are useful as chain transfer reagents for fluoroelastomers and in the free radical polymerization of fluorinated vinyl monomers. See U.S. Pat. Nos. 4,243,770 and 4,361,678. The reaction of CF.sub.2 I.sub.2 with olefins allows the stepwise addition to the chain, thereby providing controlled chain growth. The production of these diiodoperfluoroalkanes at relatively high yields has been hampered in the past by the lack of a method by which to produce relatively high yield and purity CF.sub.2 I.sub.2. However, as described in commonly held U.S. patent application Ser. No. 60/012,160, filed Feb. 23, 1996, a priority document listed for PCT International Publication No. WO 97/30957, CF.sub.2 I.sub.2 can be produced in sufficiently high yields to facilitate the reactions described below.
Commonly held U.S. Pat. No. 5,504,248 describes the production of diiodofluoroalkanes by reacting I.sub.2 with hexafluorocyclopropane. This process involves a relatively complex ring-opening reaction, and uses relatively expensive starting materials.
Elsheimer, et al., J. Org. Chem. 1984, 49, pp. 205-207, discloses reactions of CF.sub.2 1.sub.2 with hydrocarbon olefins to produce iododifluoroalkenes viaphotolysis, or diiododifluoroalkanes via reactions catalyzed by peroxide at temperatures less than 100.degree. C. The use of peroxides to form the diiododifluoroalkanes could result in the production of other reaction products, which would have to be separated from the desired products, thus adding an additional step, as well as the associated costs involved with such purification.
Many citations are found throughout the literature describing diiodofluorinated compounds, but interest continues in developing new, efficient processes for producing selected diiodofluorinated compounds.